Faulty Control Board - Stud Welder

[AtharMasoodCAE]

Hi,

I am Athar Masood from Pakistan. I just recently bought a stud welder from junk yard auction. The problem is that all the panel LED's are working, and I can hear some humming sound from the power transformer, but it isn't charging the capacitors. There are two capacitors both 66000uF 110V. The charging voltage is directly taken from the power transformer controlled by a control board via an LED.

The capacitors are getting a constant voltage of 35V from the supply line whereas it should be 50 ~110v range. The control PCB is attached. The welder says 1035 on it's front panel. It has German written on the face plate. I have no information about it's make. Please help.

 

[AtharMasoodCAE]

The Welder Face Panel

Here is the face plate:

 

[AtharMasoodCAE]

Help please

Please help!

 

[Wozzaaah]

Athar, please could you stop bumping your posts and be a little more patient? If anyone is able to help you with your problem they will do so!
Thanks.

 

[AtharMasoodCAE]

No Bump

Sorry, but where are the experts? . No body willing to help me?

 

[Wozzaaah]

Athar, this is a diy welding forum, not an elecronics repair one.
It's not a case of people being unwilling to help, more likely unable.
There are one or two welding distributors and one or two electronics engineers who are members, if any of them can possibly advise you then they will, it all depends on whether they have any knowledge of your machine and the board in question.
Please be patient, bumping posts several times in a day is totally unnecessary.

 

[eddie49]

What data do you have to suggest that the charging voltage should be 50 to 110v ?
If the main caps are 110 VW, it is not likely that they would be used at more than two-thirds of that - about 70v max.
If the caps are at least getting charged to 35v, have you tried using the welder at that voltage ?
Is the power supply switched-mode, or a simple transformer/rectifier ? If the latter, it should be easy to troubleshoot and decide if the 35v you have is valid.
I don't see any components on the PCB that you have shown which would affect that supply voltage.
Do you have the stud-setting pistol that plugs in to the multi-pin socket on the PCB ?
The German words are On, Ready, Charge, Stop, Energy ( Power ), Split ( Gap ), Start, and Pistol.
Does the yellow Charge LED come on ( or go out ) after some time - indicating that the caps are charging ?
What, if any, effect does the 4K pot have ?

 

[AtharMasoodCAE]

Details

Thanks @eddie49

It should be working around 100V as the supply is through a transformer (220V down to 110V+24V), and supplied via a thyrister. The thyrister is gated through the shown PCB. The yellow LED blinks at a frequency set by the variable and goes OFF after the capacitors are charged according to the setting.

I have checked the welder at 35V, there is a very weak weld spark. I should be working around 50~100V as charging the caps at 50V produces decent spark (supplied 50V directly to the capacitors).

Regards

 

[eddie49]

Athar, it sounds like the board and timer and thyristor are working correctly, and as you said, the charging voltage is just too low.
Perhaps one half of the rectifier is open ( i.e. an O/C diode ), so it is only passing alternate half-cycles.
In case there is a short pulling down the DC supply, you could also try disconnecting each of the two capacitors in turn, or checking the voltage with no load at all.

 

[AtharMasoodCAE]

@eddie49

Sadly, I gave it to one of my friend for repair, and now everything stopped working.....It would be of great help if someone can provide me a schematic diagram of such a welder as three components have been lost, a burnt resistor, a head-less transistor and an un-identified zener diode....!

Could you arrange me a schematic?

 

[eddie49]

Oh dear, that can happen !
No, I don't have a circuit diagram. The board is not too complex, and only single-sided, so it would be possible to reverse-engineer the circuit ( i.e. trace the tracks ). That would allow a good guess at the values of the destroyed components.
Alternatively, since you bought one, there must be other stud welders of this model around, which you could maybe get to look at.